Re: C11 / VS 2019

Peter Eisentraut <peter(at)eisentraut(dot)org> writes:
> On 04.06.25 08:15, Peter Eisentraut wrote:
>> For an explanation, the background is that MSVC has a "traditional"
>> preprocessor and a new "conforming" one.  The latter is available
>> starting in VS 2019, but it's not the default.  We have some code,
>> especially around __VA_ARGS__ that specifically caters to this
>> traditional preprocessor.

> I have committed this.

Buildfarm member drongo has been failing in initdb since 1 July:

selecting default time zone ... UTC
creating configuration files ... ok
running bootstrap script ...
----------------------------------- stderr -----------------------------------
TRAP: failed Assert("SysCache[cacheId]->cc_nkeys == 2"), File: "../pgsql/src/backend/utils/cache/syscache.c", Line: 237, PID: 2684
child process was terminated by exception 0xC0000409

While there are 19 new commits in the first run that shows this
failure [1], the only one that looks plausibly related is

8fd9bb1d965 Tue Jul 1 07:41:40 2025 UTC Enable MSVC conforming preprocessor

because that changed our implementation of VA_ARGS_NARGS(), which is
what's used to compute the cc_nkeys fields for syscaches.

My conclusion is that Microsoft's "standards conforming" preprocessor
is not so standards conforming as all that.

regards, tom lane

[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=drongo&dt=2025-07-01%2016%3A09%3A21